The present invention relates to a spindle and a method for driving the spindle equipped with a rotary mechanism to be used as a rotating and cutting/grinding apparatus in a cutting or grinding process. The spindle accompanied by no mechanical loss resulting from friction and no backlash of a feed mechanism due to the employment of a magnetic bearing designed to support a rotary shaft in space in a contactless manner by the suction forces of electromagnets.
Conventionally, in order to provide a rotating and cutting/grinding apparatus for use in the cutting or grinding process, a rotary mechanism composed of rotary supporting devices such as bearings or the like and a cutting or grinding mechanism comprised of a sliding section and a driving section, both mechanisms formed in separate units, are coupled by a coupling device, to constitute the rotating and cutting/grinding mechanism.
A rotating and cutting/grinding apparatus generally employed will be depicted hereinbelow. FIG. 10 is a diagram of a rotary cutting or grinding mechanism using a grinding wheel 9. In FIG. 10, the rotation of a cutting or grinding motor 2 mounted at a fixed surface 1 of a slide is shifted in the backward-and-forward direction via a driving device 3 such as a ball screw, etc., to thereby move a sliding surface 4 of the apparatus back and forth as a cutting or grinding mechanism. At the same time, while bearings 6 of a main shaft are inserted into a housing 5 to support a rotary shaft 7, the rotary shaft 7 is driven by a motor 8 of the main shaft to thereby rotate the grinding wheel 9 as a function of a rotary mechanism.
Meanwhile, the twist or deflection of the driving device due to the weight of the slide is arranged to be reduced in a manner, e.g., shown in FIG. 11. That is, the rear portion of a moving part 10 supported by elastic hinges 18 is moved in its longitudinal direction by impressing a voltage to a piezoelectric driver 11. In this manner, cutting or grinding is carried out while the twist or deflection of the driving device is reduced.
In the former arrangement using a slide, however, the cutting or grinding amount becomes erroneously varied due to the clearance of the coupling part of the driving device as well as the twist or the like resulting from the driving resistance of each part. High-speed operation is hence unreliable.
In the latter method using elastic hinges, not only does the weight of the movable part become large, but the load necessary to shift the hinges is increased. Therefore, the method is applicable only to a driving part of relatively small size.
Since the rotary supporting mechanism and the cutting or grinding mechanism are constructed separately in the above prior art which inevitably gives rise to the increase of the weight of the movable part, such an inconvenience is brought about that each part is undesirably twisted. Likewise, with the employment of the elastic hinges, the weight of the movable part is increased and the shifting load of the hinges must be large, thus causing difficulties in the application of the method to a cutting or grinding mechanism with a rotary supporting mechanism.